1. Field of the Invention
The invention relates to an ink cartridge for supplying ink to a recording apparatus.
2. Description of Related Art
JP-2001-113723 (especially FIG. 4) discloses an ink cartridge for supplying ink to a recording apparatus such as inkjet printer, which cartridge is constructed such that the ink does not leak upon removal of the cartridge from the recording apparatus. This ink cartridge has an ink chamber where the ink is stored, an ink outlet through which the ink is supplied to the exterior, and an ink communication chamber.
In the ink communication chamber is accommodated a valve member, and in the ink outlet is fitted a tubular packing. The valve member is biased by a compression spring and held in contact with the tubular packing so as to close an ink passage, thereby preventing leakage of the ink from the ink chamber. When the ink cartridge is attached to the recording apparatus, an ink inlet tube disposed on the recording apparatus enters the tubular packing to push the valve member to the side of the ink chamber against the biasing force of the compression spring, so as to open the ink passage and enables ink supply.
However, in the ink cartridge described above, the displacement of the valve member is realized by use of the compression spring, and thus an internal structure of the ink cartridge using the compression spring is complex. Further, the compression spring is of metal and the ink cartridge can not be discarded as it is. That is, upon disposal of a used ink cartridge, the compression spring should be detached from the ink cartridge to be discarded separately from the other part of the ink cartridge, thereby pushing up the cost of the disposal.
To solve the above-described problems, the present applicant has proposed to replace the compression spring with a biasing member formed of an elastic material to integrally include an elastic side wall portion that surrounds the valve member and is capable of deforming in a direction of the displacement of the valve member, and an engaging portion that extends inward from an end of the side wall portion to be in contact with a surface of the valve member which surface is opposite to a valve hole. An elastic, contracting force of the side wall portion biases the valve member to a position to close the ink passage or the valve hole.
The employment of the biasing member enables to omit the compression spring, thereby preventing the internal structure of the ink cartridge from being complex. Further, being formable of an elastic material such as rubber, the biasing member needs not to be detached from the ink cartridge upon disposal of the ink cartridge. Thus, the disposal cost is not increased.
When the ink cartridge including the biasing member is attached to the recording apparatus, the ink inlet tube disposed on the recording apparatus pushes the valve member as closing the ink passage to displace the valve member by stretching the side wall portion of the biasing member against the elastic biasing force thereof so as to open the ink passage. Hence, a space for allowing expansion of the side wall portion of the biasing member should be provided.
However, a user may attach the ink cartridge to the recording apparatus in an improper manner or tamper with the ink cartridge, such that the valve member is pushed by an amount larger than a normal amount by which the valve member is expected to be pushed, or in a direction different from a normal direction in which the valve member is expected to be pushed. In the event of this, the side wall portion of the biasing member is stretched excessively, or the engaging portion is deformed into an irregular shape by locally deforming more at a part than the other part, resulting in disengagement of the valve member from the engaging portion of the biasing member, that is, the valve member gets out of the biasing member into the above-mentioned space and become incapable of getting back to a position to close the ink passage in a valve chamber defined inside the biasing member. This causes leakage of the ink from the ink cartridge and evaporation of water or other components from the ink.